Brachytherapy (radioactive seeds), thermotherapy (heating), and cryotherapy (freezing) are proven therapies for tumors, both benign and malignant. Although the effectiveness of these treatments has been established, the risks associated with these treatments prevent or at least inhibit the wide application that they might otherwise achieve. The risks in each instance are related to the difficulties in achieving full control and accurate monitoring of the treatment. The risks of damaging surrounding tissues are present in every case, potentially catastrophic and require great care and experience to control.
In this regard, these therapies are frequently performed in conjunction with an ultrasound imaging probe placed in the rectum to monitor treatment. A template grid arrangement, which is kept in precise linear orientation with the ultrasound probe, must be accurately oriented adjacent the perineum in relation to the prostate, and locked in position throughout the procedure to achieve optimum results. Precise and reproducible orientation and positioning of the ultrasound imaging probe in the rectum is a key element in the clinical application of these therapies.
A number of prior art devices provide the necessary orientation and positioning. For example, U.S. Pat. No. 5,931,786, the contents of which are incorporated herein by reference, discloses a template grid support or mount and an ultrasound probe support (collectively referred to as a stepper) with a stepping function for precision axial longitudinal movement and rotation of an ultrasound probe. During a procedure, the ultrasound probe is manually inserted into the rectum and, once the desired orientation is achieved as viewed and confirmed by the monitored ultrasound images, the probe is connected to the stepper (which is typically attached to a support stand). Alternatively, if the support stand has suitable mobility, the stepper and probe can be attached to the support stand before insertion into the rectum. With the support stand set in a fixed mode, a range of positively controlled microadjustments may be used to achieve an ideal probe or instrument orientation for starting the procedure.
The template grid mount supports a needle guiding template grid which may be moved longitudinally along the centerline axis of the ultrasound probe while keeping a constant radial distance from this same axis. The stepping function allows precise, independent, and reproducible longitudinal movement of the ultrasound probe while keeping it in accurate radial position in relation to the grid. The rotation function of the stepper permits free axial rotation of the ultrasound probe and easy placement and removal of the ultrasound probe from the stepping device while retaining position of the stepping function and the template grid.
Thus, the stepper allows rotation and longitudinal movement along the axis of the ultrasound probe. However, no vertical adjustments of the ultrasound probe with respect to template grid is possible. Such vertical adjustments could be advantageous for improving treatment efficacy and safety. As previously noted, the major concern and risk of morbidity from cryotherapy and thermotherapy is thermal damage to the rectal area. This worry often limits effective treatment at the posterior margins of the prostate. In the case of cryotherapy, freezing this area is required and if the freezing is too aggressive a postoperative fistula from the prostate to the rectum may result from also freezing the rectal wall.
These concerns have been dealt with clinically by using a number of techniques to reduce pressure on the anterior rectal wall, thereby improving blood flow and decreasing the chances of freezing this vital area: removing the ultrasound probe during freezing or; placing weights on the probe to pull it posteriorly away from the anterior rectal wall during freezing. The latter technique is preferred because it maintains some ultrasound visibility. These techniques may be enhanced by injecting warm saline into the rectum during freezing of the prostate or by injecting fluid in the potential space between the posterior prostate and anterior rectal wall to create additional separation prior to freezing the prostate. However, all these current methods for improving safety require actively moving the ultrasound probe away from the anterior rectal wall using methods that are clumsy, time consuming and that significantly compromise good visibility using the ultrasound image. The proposed invention described herein provides a convenient, controlled and safe method for moving the ultrasound probe away from the anterior rectal wall when desired with minimal compromise of the ultrasound images and no disruption of the surgical field, as well as exact restoration of the initial imaging position at the completion of the freezing cycle.
As the previous discussion illustrates, a need for an improved stepper exists.